This invention relates to low-foaming surfactant mixtures containing hydroxy mixed ethers and special other low-foaming nonionic surfactants and to the use of these low-foaming mixtures as surfactants in industrial and domestic cleaning compositions. The present invention also relates to the use of the low-foaming mixtures in rinse aids, more particularly for dishwashing machines, and to rinse aids containing the hydroxy mixed ethers.
For surfactants which are intended for use in institutional and industrial cleaning compositions, it is crucially important that they generate little foam under the particular in-use conditions in order to guarantee a trouble-free cleaning process. However, domestic cleaning compositions, for example wax-containing high-shine floor cleaners, should also generate little foam so that no unattractive wax bubbles are left behind after drying.
In many cases, however, surfactants are not only expected to have little or no tendency to foam, they are also expected to show additional properties, such as good wetting properties, alkali stability and favorable rinse-off behavior. For washing bottles in the beverage industry, for example, the surfactants are also expected to be stable under highly alkaline conditions, i.e. they should not form any foaming degradation products. In addition, in industrial cleaning processes in the metal industry, they are also expected to show very good wetting properties so that drawing and rolling oils can be satisfactorily removed. Favorable rinse-off behavior is an important factor, for example, in the spray cleaning of cars where, after the actual washing process, the surfactants have to be completely rinsed off together with the soil with only a little water in a very short time. In addition, the water is intended to drain from the bodywork in the form of a thin coherent film so that no water droplets, streaks or films are left behind during the following brief drying process.
In machine dishwashing, too, the special rinse aids used in the so-called clear-rinse cycle are expected to show good wetting properties so that the surface tension of the rinsing water used can be reduced to such an extent that it drains like a film from the tableware and, after drying, does not leave behind any visible residues, such as lime stains. In addition, the rinse aids are expected to be low-foaming in view of the vigorous movement of the wash liquor in dishwashing machines.
DE-A1 37 23 873 discloses hydroxy mixed ethers which may be used either on their own or in combination with fatty alcohol alkoxylates in rinse aids for machine dishwashing. These hydroxy mixed ethers are prepared by reacting C10-18 epoxides and alcohol ethoxylates ethoxylated with 7 to 30 moles ethylene oxide.
DE-A1 37 23 323 also discloses hydroxy mixed ethers which may be obtained by reacting C8-18 epoxides and alcohol alkoxylates alkoxylated with up to 30 moles ethylene oxide and/or propylene oxide. According to this document, the hydroxy mixed ethers may be used on their own as foam-suppressing additives in low-foaming cleaning compositions.
Finally, International patent application WO 96/12001 discloses hydroxy mixed ethers which are obtained by reacting C4-16 epoxides with alcohol alkoxylates, the alcohols being derived from monohydric to trihydric alcohols which have been alkoxylated with 0 to 5 mole propylene oxide and 1 to 30 mole ethylene oxide or only with 1 to 35 mole propylene oxide. These hydroxy mixed ethers may be used as a surfactant mixture for the cleaning of hard surfaces, more particularly tableware, or in the form of liquid blends as rinse aids.
The problem addressed by the present invention was to provide surfactant mixtures for cleaning various surfaces, such as glass, tableware, metal surfaces, plastics, stone floors and painted metal surfaces. The surfactant mixtures would have little tendency to foam, but at the same time would show favorable rinse-off behavior and an improved clear drying effect so that they would not leave any troublesome visible stains behind on the cleaned surface. Finally, the surfactant mixtures would have good low-temperature behavior so that no troublesome phase separation would occur either at the occasionally high in-use temperatures or at the occasionally low storage temperatures.
The complex problem stated above has been solved by mixtures containing hydroxy mixed ethers and other special low-foaming nonionic surfactants.